Dual Antennas and Antenna Amplifiers
Two Antennas may be used to cover different areas of a large installation by combining them together using
a TV-type splitter/combiner. They are bidirectional, but are usually labelled for splitter use (1 input, 2
outputs); when used as combiners, consider them to have 2 inputs and 1 output. The splitter/combiners
that are commonly available are typically rated for 5-900 MHz, 50-500 MHz, 50-900 MHz, etc. (some are
not rated at all). The high frequency limit does not matter here, but the low end does. Since the lowest TV
channel (Ch2) is in the low 50 MHz range, many devices are not rated below that point. Vaux uses a 27 MHz
control band, which requires a combiner rated down below that point — the Vaux Model AACC-3 Dual
Antenna Combiner is rated appropriately. Be sure to not use a UHF/VHF band splitter, or a CATV line tap
here (they can look the same as a splitter/combiner).
Note that a 2-port combiner will typically have a 3 dB loss on each antenna input, and will provide 20 dB or
more of port isolation. The port loss may not affect coverage adversely if you are using good antennas, but
if maximum coverage is needed, the Vaux Antenna Preamp (APA-1) may be added between the Combiner
and the Controller. The example below shows a typical dual-antenna installation: a Base-Loaded Coax
Antenna is used for primary coverage near the Controller, while a Folded Dipole Antenna provides remote
coverage for distant areas of the home.
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